Question

A jogger desires to run a certain course in 1/4 less time than she usually takes; by what percent must she increase her average running speed to accomplish this goal?

Answer 1

In movement problem, the speed is inversly proportional to the time of object moving.

v1 is regular speed and responding time is t1
v2 is a goal-speed and responding time is t2
t1=4, t2 is less than t1 1 unit, t2=3

v1/v2 = t2/t1 = 3/4
v2=4/3 *v1

Percent increase 33 1/3%